This invention relates to a light-sensitive silver halide photographic material, more particularly to a light-sensitive silver halide photographic material having high sensitivity and improved pressure fog.
In recent years, there is an increasing demand for higher image quality of light-sensitive silver halide photographic material with higher sensitization of color negative film and smaller formatting, as is well known in the art. In response to these demands, there have been abundantly made studies about core/shell type emulsions having silver iodide phase with high silver iodide content. Particularly, core-shell type silver iodobromide emulsions having high silver iodide content phase of 15 mole % or more internally of grains have attracted attention abruptly for use in color negative film.
In connection with such current demand for higher sensitization, higher image quality formation, a demand for strengthening of pressure characteristics in light-sensitive silver halide photographic material has been increased more than before. Although improvement of pressure characteristic has been investigated in the prior art by various means, the point of view that the method to improve stress resistance of silver halide grain itself is practically more preferable and greater in effect than the method of adding a plasticizer, etc. is prevailing. As the prior art born from such standpoint, there have been known, for example, Japanese Provisional Patent Publications No. 35726/1985, No. 147727/1985 and No. 198324/1985. All of these are core/shell emulsions, containing phases applied with halogen substitution with iodides internally of the grains. The silver halide grains obtained according to these methods are improved in pressure characteristics, but the extent of such improvements cannot be said to be satisfactory.